(1) Field of the Invention
This invention relates to material for non-magnetic substrates used for sliders of the magnetic heads.
(2) Description of the Prior Art
Magnetic heads used for magnetic disks ordinarily have a structure as disclosed, for example, in Japanese Patent Publication No. 57-569. In these floating type magnetic heads, a magnetic core made from a magnetic material of high permeability is fixed to the rear end portions of sliders each comprising a magnetic or non-magnetic substrate. On the lower sides of the sliders, the magnetic core has a gap for magnetic transduction. The magnetic core further has a winding for electromagnetic transduction, whereby a magnetic transducer is formed. A floating type magnetic head having such a structure is in light contact with a magnetic disk due to a spring action when the magnetic disk is stopped. When the magnetic disk is rotating, the air around the surface of the magnetic disk also moves pushing up the lower sides of magnetic head sliders.
The transducer portion of magnetic head is made, in many cases, from a soft ferrite such as Mn-Zn ferrite or Ni-Zn ferrite. When the recording density of magnetic disk is increased, it is required that the width of magnetic core and the length of the gap for magnetic transduction be made smaller, and at that time, the magnetic core is made from a magnetic thin film of permalloy or amorphous metal made by sputtering, etc. There are cases that one magnetic core is made from a soft ferrite and the other core from a magnetic thin film. When a thin film core is used a thin film of insulating material such as Al.sub.2 O.sub.3 may be applied on both the thin film magnetic core and sliders to obtain electrical insulation between a winding for the electromagnetic transduction and the thin film core or between coils for electromagnetic transduction. When non-magnetic slider substrates are made from a material of relatively low electrical resistance a thin film of insulating material may be applied on the sliders to obtain insulation between the sliders and the magnetic thin film core to form a magnetic transducer.
Such a magnetic head does not contact the magnetic disk when the magnetic disk is rotating because the head is buoyant due to the flow of air. The magnetic head, however, comes in contact with the magnetic disk when the magnetic disk starts or stops rotation. For example, when the magnetic disk stops rotation, the magnetic head comes in contact with the magnetic disk as follows. As the magnetic disk reduces its rotation speed, the flow speed of the air around the surface of the magnetic disk becomes slow. When buoyancy for the magnetic head is lost, the magnetic head hits the magnetic disk. As a reaction, the magnetic head jumps up and drops on the disk again. Such a movement is repeated many times (the magnetic head appears to be dragged on the magnetic disk) and there comes a final stop. Any magnetic head must be able to withstand a shock at the start or stop of the magnetic disk and such an ability of a magnetic head at such times is called its CSS resistance (CSS stands for contact-start-stop).
In order for a magnetic head to have a superior CSS resistance property, the slider portion of the magnetic head must have excellent slidability. Further, the slider portion must be flat and free from pores and have good wear resistance.
The slider portion of magnetic head has a very complex structure as shown, for example, in Japanese Patent Laid-open No. 55-163665. In order to produce a slider of such a structure at a high productivity, the material for slider must have good machinability. Further, it is desirable that chipping of the slider material during machining be as little as possible. For this purpose, it is desirable that the slider material have crystal grain particles as small as possible.
Such a magnetic head as described above its disclosed in Japanese Patent Laid-open No. 55-163665 mentioned above. The slider of this magnetic head is made from a mixture of Al.sub.2 O.sub.3 and TiC and the weight ratio of Al.sub.2 O.sub.3 to TiC is in a range of 60:40 to 80:20. Al.sub.2 O.sub.3 -TiC ceramics have some disadvantages for example, the low density and tendency of chipping because of low affinity between Al.sub.2 O.sub.3 and TiC particles. When chipped, the chips are large because of the large grain size of 4 to 5 .mu.m.